Frictional gear backlash eliminating means in sheet fed rotary printer

ABSTRACT

Sheet-fed rotary machine for letterpress or offset printing includes at least one sheet transfer drum for transferring a suitably adjusted sheet from a sheet feed table to the grippers of an impression cylinder or from the impression cylinder of one printing stage to an impression cylinder of a succeeding printing stage, the sheet transfer drum being provided with an annular raceway or travel ring disposed in pressure contact with a corresponding annular raceway provided for an adjacent drum or cylinder.

United States Patent Sternberg [4 Aug. 1, 1972 [54] FRICTIONAL GEAR BACKLASH [56] References Cited ELIMINATING MEANS IN SHEET FED UNITED STATES PATENTS ROTARY PRINTER 2 554 904 5/1951 H ld 101/183 X arro 1 Inventor Hubert Stemberg, fleldelberg, 2,790,385 4/1957 Kaldschmidt ..101/232 Germany 2,940,387 6/1960 Pritchard ..l0l/183 [73] Asslgnee: g g i z f igfig Primary Examiner-William B. Penn 'engese e1 e er- Assistant Examiner-E. M. Coven many Attorney-Curt M. Avery, Arthur E. Wilfond, Herbert [22] Filed: July 1, 1969 L. Lerner and Daniel J. Tick [21] App]. No.: 838,090 5 ABSTRACT t Sheet-fed rotary machine for letterpress or offset [30] Foreign Application Pri rity ata printing includes at least one sheet transfer drum for transferring a suitably adjusted sheet from a sheet feed July 1968 Germany 'f' 17 61 7800 table to the grippers of an impression cylinder or from the impression cylinder of one printing stage to an im- [52] US. Cl. ..101/232, 101/183, 101/246 pression cylinder of a succeeding printing Stage, the [51] Int. Cl. ..B4lf 5/02,B41f 13/16 sheet t f drum b i id d i h an n l Field 0f Search 2, 2 6 raceway or travel ring disposed in pressure contact with a corresponding annular raceway provided for an adjacent drum or cylinder.

1 Claim, 2 Drawing Figures FRICTIONAL GEAR BACKLASH ELIMINATING MEANS IN SHEET FED ROTARY PRINTER My invention relates to sheet-fed rotary machine for letterpress or offset printing and, more particularly, to such a machine having one or more sheet transfer drums for transferring an aligned or adjusted sheet from a sheet feed table to the grippers of an impression cylinder or from the impression cylinder of one printing stage or mechanism to an impression cylinder of a succeeding printing stage or mechanism.

In sheet-fed rotary machines of this general type, the opening and closing movements of the various gripper bars or systems in the impression cylinders produce vibrations in the sheet transfer drums or advance gripper systems which disadvantageously affect the printing results.

These vibrations are especially disturbing in the case of rotary offset printing machines because they affect the meshing of the gears between the plate and blanket cylinders of the offset machines. A change in the location of the teeth flanks or surfaces of the gears at this location produces in an offset press an undesired doubling or mackling, resulting in uncontrollable deviation in the color tone values.

To eliminate the foregoing difficulties, various devices have become known, such as resiliently mounted toothed segments, for example, which have been provided at the impression cylinders and the sheet transfer drums to prevent a change in position of the teeth flanks or surfaces during the time the sheet is being transferred. In addition thereto is the use of resiliently mounted by-running gears on the shafts of the cylinders and the sheet transfer drums.

It has furthermore become known to eliminate the disruptive forces, for example, due to the advance gripper movement by providing controlled springy thrust bearings for the required tension or compression springs. Also, double eccentric gears formed of main and by-running eccentrics have been employed heretofore for largely eliminating the doubling or mackling difficulties. The doubling difficulties are manifested especially in autotype printing by the formation of clearly visible stripes on the sheet being imprinted.

To eliminate the aforedescribed disturbances from the heretofore known devices, very precise and expensive gears or toothed segments, for example, have been employed heretofore. Other known measures for removing the disturbances are the provision of costly double gears or double eccentric gears. To accommodate the additional gear member, additional space, for example on the side, is required outside the machine frame. This construction proves to be especially costly when lubrication of the added gear member is necessary.

It is accordingly an object of my invention to provide sheet-fed rotary machine for letterpress or offset printing which avoids the aforementioned disadvantages of the heretofore known machines of this general type.

More specifically, it is an object of my invention to effectively damp or minimize disturbing vibrations originating, for example, from opening and closing movements of the various gripper systems.

It is a further object of the invention to provide sheet-fed rotary machine for letterpress or offset printing which is of considerably simpler construction than the heretofore known machines of this type, and is also less demanding with regard to manufacturing costs and maintenance.

With the foregoing and other objects in view, in accordance with my invention, I provide the sheet transfer drums with annular raceways or travel rings in prestressed mutual rolling engagement with corresponding annular raceways or travel rings provided for adjacent drums or cylinders.

In accordance with a further feature of my invention, the travel rings are hardened and polished and the driving drum is several hundredths of a millimeter larger in diameter than the driven drum or the cylinder.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in sheet-fed rotary machine for letterpress or offset printing, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a schematic elevational view partly in section of a two-stage or double printing mechanism of a two-color offset machine; and

FIG. 2 is a longitudinal view of an impression cylinder cooperating with a sheet transfer drum.

Referring now to the drawing and first particularly to FIG. 1 thereof, there is shown a two-color offset machine, in the side-walls 1 of the first of the two stages thereof, a plate cylinder 2, a rubber blanket cylinder 3 and an impression cylinder 4 are mounted. The impression cylinder 4 is in gear-meshing engagement with sheet transfer drums 5 and 11, as can be concluded more readily from FIG. 2. A motor M and a conventional gear transmission system noted generally by the reference numeral 25 drive the transfer drum 5. The drum 5 with a set of grippers 6 serves for transferring an aligned or registered sheet from the sheet feed table 8 through the advance grippers 7. The grippers 4 take over the sheet from the grippers 6 of the transfer drum 5, guide the sheet past the inked rubber blanket of the cylinder 3, and a set of grippers 9 of the transfer drum 11 take over the sheet and release it to the set of grippers 10 of the impression cylinder 12 in the second printing stage or mechanism. After the sheet has been imprinted with the second colored ink, it is taken over by a set of grippers or gripper bars 13, mounted on a rotating chain delivery system or conveyor 14, which advances the imprinted sheet in a conventional manner to a location at which it is stacked. The line of contact between the plate cylinder 2 and the blanket cylinder 3 is identified by reference numeral 15. The first printing stage or mechanism is provided with conventional moistening mechanism 16 and inking rollers 17. The second printing stage or mechanism is similarly provided with moistening and inking rollers which are, however, not further identified in FIG. 1.

In order to prevent the impacts or shocks produced by the opening and closing movements of the sets of gripper bars during sheet transfer from one cylinder or from one drum to another to be spread or imparted to the line of contact between the plate cylinder 2 and the blanket cylinder 3, the cylinder 4, l2 and sheet transfer drums 5 and l 1, according to my invention, are provided with annular raceways or travel rings which are in mutual rolling engagement or in pressure contact. Whereas so-called Schmitz rings are provided on the cylinders 2 and 3 and can roll on one another in pressure contact, there can be no discussion of Schmitz rings with regard to annular raceways or travel rings on the transfer drums 5 and 1 1 since they have nothing to do with the pressure itself. Consequently such members are referred to herein as annular raceways or travel rings which are in mutual rolling engagement or in pressure contact. As to further details regarding Schmitz rings, otherwise known as bearers or cylinder bearers, reference can be had to Pat. No. 3,049,996 of R. H. Downie.

An added feature of my invention is that this travel ring is installed at the cylinders 4 and 12 and transfer drums 5 and l l with a slight difference in outer diameters of several hundredths of a millimeter. Beginning with the driven cylinder 4, whose travel ring, for example, has a given measured diameter with i 0 tolerance, every travel ring of the succeeding drums or cylinders is ground or polished so that its diameter is about 0.02 mm greater than that of the preceding one with which it is in pressure contact. This produces per rotation an additional frictional force directed toward the profiles of the gear teeth, whereby a backlash of 0.0628 mm arises when the tolerance maintained is 0.02 mm. A change in location of the teeth profiles due to the impacts or shocks is thus counteracted by this further feature in addition to the rolling contact effected under pressure between the travel rings.

FIG. 2 shows the impression cylinder 4 as well as the transfer drum 11 in longitudinal view. In a conventional manner, the cylinder 4 and drum 11 are mounted in the side walls 1 and 1'. Travel rings 18 and 19, on the one hand, and 20. and 21, on the other hand, are firmly fastened with screws to both sides respectively of the impression cylinder 4 and the transfer drum 11. Meshing gears 22 and 23 are securely mounted respectively on the shafts of the impression cylinder 4 and the transfer drum 1 l. The gears 22 and 23, which as seen in FIG. 2 are matching, of equal pitch diameter, are located outside the frame walls of the printing press and travel through a non-illustrated lubricating oil bath. Laterally adjustable support rings 24 are provided on the transfer drum 11 for supporting the imprinted sheet. The support rings 24 are for the most part laterally adjustable so as to come into contact with only those margins or regions of the imprinted sheet that are free of print.

The critical location for the formation of the aforementioned doubling or mackling of the contours of an imprinted picture or the like is in the line of contact 15 between the plate cylinder 2 and the blanket cylinder 3. The opening and closing movements that are to be effected in a conventional manner for the sets of gripper bars 4', 6, 9, 10 and 13 which transport the sheets and whose regulation must be carried 9 t in fraction of secon cause impacts or shocks Wl'llC produce vibrations. The shocks and vibrations become increasingly greater, the faster the printing machine operates. These shocks and vibrations spread or are imparted to the line of contact 15 and can have an undesirable effect on the gears due to change in location of the gear teeth flanks, because gears must have play of several hundredths of a millimeter between the teeth thereof. The disturbance has a special effect if the printing press is being operated without any Schmitz ring pressure being applied between the plate cylinder 2 and the rubber blanket cylinder 3. Many printers prefer operating without Schmitz ring pressure since such operation has the advantage of shortening the make-ready time.

I claim:

1. In a sheet-fed rotary machine for letter-press or offset printing, an impression cylinder, at least one sheet transfer drum disposed upstream of said impression cylinder in direction of feed of a sheet through the machine, means for driving said transfer drum so as to transfer a sheet from a given location to said impression cylinder, means cooperating with said impression cylinder for imprinting a sheet thereby, gripper means located at the peripheral surface of said impression cylinder for gripping the sheet being transferred by said sheet transfer drum and disposing it on said impression cylinder, and means connecting said transfer drum to said impression cylinder so that said impression cylinder is driven by said transfer drum, said driving means comprising a pair of parallel shafts on which said sheet transfer drum and said impression cylinder are mounted, respectively, and a pair of matching intermeshing end gears respectively carried by said shafts, said sheet transfer drum and said impression cylinder being provided with respective travel rings having a smooth surface of wear-resistant hardness, respectively, in pressure contact with one another, the travel ring of said driving transfer drum having a diameter at least about two hundredths of a millimeter greater than that of the travel ring of said driven impression cylinder. 

1. In a sheet-fed rotary machine for letter-press or offset printing, an impression cylinder, at least one sheet transfer drum disposed upstream of said impression cylinder in direction of feed of a sheet through the machine, means for driving said transfer drum so as to transfer a sheet from a given location to said impression cylinder, means cooperating with said impression cylinder for imprinting a sheet thereby, gripper means located at the peripheral surface of said impression cylinder for gripping the sheet being transferred by said sheet transfer drum and disposing it on said impression cylinder, and means connecting said transfer drum to said impression cylinder so that said impression cylinder is driven by said transfer drum, said driving means comprising a pair of parallel shafts on which said sheet transfer drum and said impression cylinder are mounted, respectively, and a pair of matching intermeshing end gears respectively carried by said shafts, said sheet transfer drum and said impression cylinder being provided with respective travel rings having a smooth surface of wear-resistant hardness, respectively, in pressure contact with one another, the travel ring of said driving transfer drum having a diameter at least about two hundredths of a millimeter greater than that of the travel ring of said driven impression cylinder. 